Novel Medium Density Polyethylene Compositions

ABSTRACT

An ethylene alpha-olefin copolymer having (a) a density of from about 0.910 g/cc to about 0.940 g/cc; (b) a weight average molecular weight of from about 150,000 g/mol to about 300,000 g/mol; and (c) a melt index at a load of 2.16 kg of from about 0.01 dg/10 min. to about 0.5 dg/min.; wherein a 1 mil blown film formed from the polymer composition is characterized by (i) a Dart Impact strength greater than about 175 g/mil; (ii) an Elmendorf machine direction tear strength greater than about 20 g/mil; and (iii) an Elmendorf transverse direction tear strength greater than about 475 g/mil.

FIELD

The present disclosure relates to novel polymer compositions and filmmade from same, more specifically to polyethylene compositions for themanufacture of medium density films.

BACKGROUND

Polyolefins are plastic materials useful for making a wide variety ofvalued products due to their combination of stiffness, ductility,barrier properties, temperature resistance, optical properties,availability, and low cost. In particular, polyethylene (PE) is one ofthe largest volume polymers consumed in the world. It is a versatilepolymer that offers high performance relative to other polymers andalternative materials such as glass, metal or paper. One of the mostvalued products is plastic films. Plastic films such as PE films aremostly used in packaging applications but they also find utility in theagricultural, medical and engineering fields.

PE films are manufactured in a variety of polymer grades that areusually differentiated by the polymer density such that PE films can bedesignated for example, low density polyethylene (LDPE), medium densitypolyethylene (MDPE) and, high density polyethylene (HDPE) wherein eachdensity range has a unique combination of properties making it suitablefor a particular application. Generally speaking, MDPE films provide abalance between resiliency and flexibility. An ongoing need exists forpolymer compositions having the desired density and balance ofproperties.

SUMMARY

Disclosed herein is an ethylene alpha-olefin copolymer having (a) adensity of from about 0.910 g/cc to about 0.940 g/cc; (b) a weightaverage molecular weight of from about 150,000 g/mol to about 300,000g/mol; and (c) a melt index at a load of 2.16 kg of from about 0.01dg/min. to about 0.5 dg/min.; wherein a 1 mil blown film formed from thepolymer composition is characterized by (i) a Dart Impact strengthgreater than about 175 g/mil; (ii) an Elmendorf machine direction tearstrength greater than about 20 g/mil; and (iii) an Elmendorf transversedirection tear strength greater than about 475 g/mil.

Also disclosed herein is an ethylene alpha-olefin copolymer having (a) adensity of from about 0.910 g/cc to about 0.940; (b) a weight averagemolecular weight of from about 150,000 g/mol to about 300,000 g/mol; and(c) a melt index at a load of 2.16 kg of from about 0.01 dg/10 min. toabout 0.5 dg/min.; wherein a 1 mil blown film formed from the polymercomposition has (i) a Dart Impact strength greater than about 200 g/mil;(ii) an Elmendorf machine direction tear strength less than about 100g/mil; and (iii) an Elmendorf transverse direction tear strength greaterthan about 550 g/mil.

Also disclosed herein is an ethylene alpha-olefin copolymer having adensity of from about 0.910 g/cc to about 0.940 g/cc; a weight averagemolecular weight of from about 150,000 g/mol to about 300,000 g/mol; amelt index at a load of 2.16 kg of from about 0.01 dg/min. to about 0.5dg/min.; a melt index at a load of 5.0 kg of from about 0.01 dg/min. toabout 1 dg/min.; a melt index at a load of 10.0 kg of from about 0.01dg/min. to about 5 dg/min; a high-load melt index at a load of 21.6 kgof from about 4 dg/min to about 25 dg/min wherein a 1-mil blown filmformed from the polymer composition has an Elmendorf tear strength inthe machine direction of from about 10 g to about 130 g as determined inaccordance with ASTM D1922.

DETAILED DESCRIPTION

Disclosed herein are polyethylene (PE) polymers, PE films, and methodsof making same. Such methods may comprise preparing a PE polymer andforming the polymer into a film. In an aspect, the PE polymer comprisesa multimodal PE resin and the film prepared therefrom may displayenhanced mechanical properties such as increased toughness and tearproperties.

The PE polymer of the present disclosure can be formed using anysuitable olefin polymerization method which may be carried out usingvarious types of polymerization reactors. As used herein,“polymerization reactor” includes any polymerization reactor capable ofpolymerizing olefin monomers to produce homopolymers or copolymers. Suchhomopolymers and copolymers are referred to as resins or polymers.

The various types of reactors include those that may be referred to asbatch, slurry, gas-phase, solution, high pressure, tubular, or autoclavereactors. Gas phase reactors may comprise fluidized bed reactors orstaged horizontal reactors. Slurry reactors may comprise vertical orhorizontal loops. High pressure reactors may comprise autoclave ortubular reactors. Reactor types can include batch or continuousprocesses. Continuous processes could use intermittent or continuousproduct discharge. Processes may also include partial or full directrecycle of un-reacted monomer, un-reacted co-monomer, and/or diluent.

Polymerization reactor systems of the present disclosure may compriseone type of reactor in a system or multiple reactors of the same ordifferent type. Production of polymers in multiple reactors may includeseveral stages in at least two separate polymerization reactorsinterconnected by a transfer device making it possible to transfer thepolymers resulting from the first polymerization reactor into the secondreactor. The desired polymerization conditions in one of the reactorsmay be different from the operating conditions of the other reactors.Alternatively, polymerization in multiple reactors may include themanual transfer of polymer from one reactor to subsequent reactors forcontinued polymerization. Multiple reactor systems may include anycombination including, but not limited to, multiple loop reactors,multiple gas reactors, a combination of loop and gas reactors, multiplehigh pressure reactors, or a combination of high pressure with loopand/or gas reactors. The multiple reactors may be operated in series orin parallel.

According to one aspect of the disclosure, the polymerization reactorsystem may comprise at least one loop slurry reactor comprising verticaland/or horizontal loops. Monomer, diluent, catalyst and optionally anyco-monomer may be continuously fed to a loop reactor wherepolymerization occurs. Generally, continuous processes may comprise thecontinuous introduction of a monomer, a catalyst, and a diluent into apolymerization reactor and the continuous removal from this reactor of asuspension comprising polymer particles and the diluent. Reactoreffluent may be flashed to remove the solid polymer from the liquidsthat comprise the diluent, monomer and/or co-monomer. Varioustechnologies may be used for this separation step including but notlimited to, flashing that may include any combination of heat additionand pressure reduction; separation by cyclonic action in either acyclone or hydrocyclone; or separation by centrifugation.

A suitable slurry polymerization process (also known as the particleform process), is disclosed, for example, in U.S. Pat. Nos. 3,248,179,4,501,885, 5,565,175, 5,575,979, 6,239,235, 6,262,191, and 6,833,415,each of which is incorporated by reference herein in its entirety.

Suitable diluents used in slurry polymerization include, but are notlimited to, the monomer being polymerized and hydrocarbons that areliquids under reaction conditions. Examples of suitable diluentsinclude, but are not limited to, hydrocarbons such as propane,cyclohexane, isobutane, n-butane, n-pentane, isopentane, neopentane, andn-hexane. Some loop polymerization reactions can occur under bulkconditions where no diluent is used. An example is polymerization ofpropylene monomer as disclosed in U.S. Pat. No. 5,455,314, which isincorporated by reference herein in its entirety.

According to yet another aspect of this disclosure, the polymerizationreactor may comprise at least one gas phase reactor. Such systems mayemploy a continuous recycle stream containing one or more monomerscontinuously cycled through a fluidized bed in the presence of thecatalyst under polymerization conditions. A recycle stream may bewithdrawn from the fluidized bed and recycled back into the reactor.Simultaneously, polymer product may be withdrawn from the reactor andnew or fresh monomer may be added to replace the polymerized monomer.Such gas phase reactors may comprise a process for multi-step gas-phasepolymerization of olefins, in which olefins are polymerized in thegaseous phase in at least two independent gas-phase polymerization zoneswhile feeding a catalyst-containing polymer formed in a firstpolymerization zone to a second polymerization zone. One type of gasphase reactor is disclosed in U.S. Pat. Nos. 5,352,749, 4,588,790, and5,436,304, each of which is incorporated by reference herein in itsentirety.

According to still another aspect of the disclosure, a high pressurepolymerization reactor may comprise a tubular reactor or an autoclavereactor. Tubular reactors may have several zones where fresh monomer,initiators, or catalysts are added. Monomer may be entrained in an inertgaseous stream and introduced at one zone of the reactor. Initiators,catalysts, and/or catalyst components may be entrained in a gaseousstream and introduced at another zone of the reactor. The gas streamsmay be intermixed for polymerization. Heat and pressure may be employedappropriately to obtain optimal polymerization reaction conditions.

According to yet another aspect of the disclosure, the polymerizationreactor may comprise a solution polymerization reactor wherein themonomer is contacted with the catalyst composition by suitable stirringor other means. A carrier comprising an inert organic diluent or excessmonomer may be employed. If desired, the monomer may be brought in thevapor phase into contact with the catalytic reaction product, in thepresence or absence of liquid material. The polymerization zone ismaintained at temperatures and pressures that will result in theformation of a solution of the polymer in a reaction medium. Agitationmay be employed to obtain better temperature control and to maintainuniform polymerization mixtures throughout the polymerization zone.Adequate means are utilized for dissipating the exothermic heat ofpolymerization.

Polymerization reactors suitable for the present disclosure may furthercomprise any combination of at least one raw material feed system, atleast one feed system for catalyst or catalyst components, and/or atleast one polymer recovery system. Suitable reactor systems for thepresent disclosure may further comprise systems for feedstockpurification, catalyst storage and preparation, extrusion, reactorcooling, polymer recovery, fractionation, recycle, storage, loadout,laboratory analysis, and process control.

Conditions that are controlled for polymerization efficiency and toprovide resin properties include temperature, pressure, and theconcentrations of various reactants. Polymerization temperature canaffect catalyst productivity, polymer molecular weight and molecularweight distribution. Suitable polymerization temperature may be anytemperature below the de-polymerization temperature according to theGibbs free energy equation. Typically, this includes from about 60° C.to about 280° C., for example, and from about 70° C. to about 110° C.,depending upon the type of polymerization reactor.

Suitable pressures will also vary according to the reactor andpolymerization type. The pressure for liquid phase polymerizations in aloop reactor is typically less than 1000 psig. Pressure for gas phasepolymerization is usually at about 200 to about 500 psig. High pressurepolymerization in tubular or autoclave reactors is generally run atabout 20,000 to about 75,000 psig. Polymerization reactors can also beoperated in a supercritical region occurring at generally highertemperatures and pressures. Operation above the critical point of apressure/temperature diagram (supercritical phase) may offer advantages.

The concentration of various reactants can be controlled to produceresins with certain physical and mechanical properties. The proposedend-use product that will be formed by the resin and the method offorming that product determines the desired resin properties. Mechanicalproperties include tensile, flexural, impact, creep, stress relaxation,and hardness tests. Physical properties include density, molecularweight, molecular weight distribution, melting temperature, glasstransition temperature, temperature melt of crystallization, density,stereoregularity, crack growth, long chain branching and rheologicalmeasurements.

The concentrations of monomer, hydrogen, modifiers, and electron donorsmay be utilized in producing these resin properties. Co-monomer is usedto control product density. Hydrogen can be used to control productmolecular weight. Modifiers can be used to control product propertiesand electron donors affect stereoregularity. In addition, theconcentration of poisons is minimized because poisons impact thereactions and product properties. In an embodiment, hydrogen is added tothe reactor during polymerization. Alternatively, hydrogen is not addedto the reactor during polymerization.

The polymer or resin may be formed into various articles, including, butnot limited to pipes, bottles, toys, containers, utensils, filmproducts, drums, tanks, membranes, and liners. Various processes may beused to form these articles, including, but not limited to, film blowingand cast film, blow molding, extrusion molding, rotational molding,injection molding, fiber spinning, thermoforming, cast molding, and thelike. After polymerization, additives and modifiers can be added to thepolymer to provide better processing during manufacturing and fordesired properties in the end product. Additives include surfacemodifiers such as slip agents, antiblocks, tackifiers; antioxidants suchas primary and secondary antioxidants; pigments; processing aids such aswaxes/oils and fluoroelastomers; and special additives such as fireretardants, antistats, scavengers, absorbers, odor enhancers, anddegradation agents.

The PE polymer may include other suitable additives. Examples ofadditives include, but are not limited to, antistatic agents, colorants,stabilizers, nucleators, surface modifiers, pigments, slip agents,antiblocks, tackafiers, polymer processing aids and combinationsthereof. In an embodiment, the PE polymer comprises carbon black. Suchadditives may be used singularly or in combination and may be includedin the polymer composition before, during or after preparation of the PEpolymer as described herein. In an embodiment, the compositionsdisclosed herein comprise less than about 1 weight percent ofnonpolymeric additives. Such additives may be added via knowntechniques, for example during an extrusion or compounding step such asduring pelletization or subsequent processing into an end use article.Herein the disclosure will refer to a PE polymer although a polymercomposition comprising the PE polymer and one or more additives is alsocontemplated.

The concentrations of monomer, co-monomer, hydrogen, co-catalyst,modifiers, and electron donors are important in producing these resinproperties. Comonomer may be used to control product density. Hydrogencan be used to control product molecular weight. Co-catalysts can beused to alkylate, scavenge poisons and control molecular weight.Modifiers can be used to control product properties and electron donorsaffect stereoregularity. In addition, the concentration of poisons isminimized because poisons impact the reactions and product properties.

Any catalyst composition capable of producing a PE polymer of the typedisclosed herein may be employed in the production of the polymer.Typical catalyst compositions that can be employed include supportedchromium catalysts, Ziegler-Natta catalysts, metallocene catalysts, orcombinations thereof. For example, a catalyst composition for theproduction of a PE polymer may include at least two metallocenes thatare selected such that the polymers produced therefrom have twodistinctly different molecular weights. The first metallocene may beused to produce the HMW component, and may be a tightly-bridgedmetallocene containing a substituent that includes a terminal olefin.The second metallocene, that may be used to produce the LMW component,is generally not bridged and is more responsive to chain terminationreagents, such as hydrogen, than the first metallocene. The metallocenesmay be combined with an activator, an aluminum alkyl compound, an olefinmonomer, and an olefin comonomer to produce the desired polyolefin. Theactivity and the productivity of the catalyst may be relatively high. Asused herein, the activity refers to the grams of polymer produced pergram of solid catalyst charged per hour, and the productivity refers tothe grams of polymer produced per gram of solid catalyst charged. Suchcatalysts are disclosed for example in U.S. Pat. Nos. 7,312,283 and7,226,886 each of which is incorporated herein by reference in itsentirety.

In an embodiment, a catalyst composition comprises a first metallocenecompound, a second metallocene compound, an activator and optionally anorganoaluminum compound. The first metallocene compound may becharacterized by the general formula:

(X¹R¹)(X²R² ₂)(X³)(X⁴)M¹;

wherein (X¹) is cyclopentadienyl, indenyl, or fluorenyl, (X²) isfluorenyl, and (X¹) and (X²) are connected by a disubstituted bridginggroup comprising one atom bonded to both (X¹) and (X²), wherein the atomis carbon or silicon. A first substituent of the disubstituted bridginggroup is an aromatic or aliphatic group having from 1 to about 20 carbonatoms. A second substituent of the disubstituted bridging group can bean aromatic or aliphatic group having from 1 to about 20 carbon atoms,or the second substituent of the disubstituted bridging group is anunsaturated aliphatic group having from 3 to about 10 carbon atoms. R¹is H, or an unsaturated aliphatic group having from 3 to about 10 carbonatoms. R² is H, an alkyl group having from 1 to about 12 carbon atoms,or an aryl group; (X³) and (X⁴) are independently an aliphatic group, anaromatic group, a cyclic group, a combination of aliphatic and cyclicgroups, or a substituted derivative thereof, having from 1 to about 20carbon atoms, or a halide; and M¹ is Zr or Hf. The first substituent ofthe disubstituted bridging group may be a phenyl group. The secondsubstituent of the disubstituted bridging group may be a phenyl group,an alkyl group, a butenyl group, a pentenyl group, or a hexenyl group.

The second metallocene compound may be characterized by the generalformula:

(X⁵)(X⁶)(X⁷)(X⁸)M²;

wherein (X⁵) and (X⁶) are independently a cyclopentadienyl, indenyl,substituted cyclopentadienyl or a substituted indenyl, each substituenton (X⁵) and (X⁶) is independently selected from a linear or branchedalkyl group, or a linear or branched alkenyl group, wherein the alkylgroup or alkenyl group is unsubstituted or substituted, any substituenton (X⁵) and (X⁶) having from 1 to about 20 carbon atoms; (X⁷) and (X⁸)are independently an aliphatic group, an aromatic group, a cyclic group,a combination of aliphatic and cyclic groups, or a substitutedderivative thereof, having from 1 to about 20 carbon atoms; or a halide,and M² is Zr or Hf.

In an embodiment of the present disclosure, the ratio of the firstmetallocene compound to the second metallocene compound may be fromabout 1:10 to about 10:1. According to other aspects of the presentdisclosure, the ratio of the first metallocene compound to the secondmetallocene compound may be from about 1:5 to about 5:1. According toyet other aspects of the present disclosure, the ratio of the firstmetallocene compound to the second metallocene compound may be fromabout 1:2 to about 2:1.

In an embodiment of the present disclosure, the activator may be a solidoxide activator-support, a chemically treated solid oxide, a claymineral, a pillared clay, an exfoliated clay, an exfoliated clay gelledinto another oxide matrix, a layered silicate mineral, a non-layeredsilicate mineral, a layered aluminosilicate mineral, a non-layeredaluminosilicate mineral, an aluminoxane, a supported aluminoxane, anionizing ionic compound, an organoboron compound, or any combinationthereof. The terms “chemically-treated solid oxide”, “solid oxideactivator-support”, “acidic activator-support”, “activator-support”,“treated solid oxide compound”, and the like are used herein to indicatea solid, inorganic oxide of relatively high porosity, which exhibitsLewis acidic or Brønsted acidic behavior, and which has been treatedwith an electron-withdrawing component, typically an anion, and which iscalcined. The electron-withdrawing component is typically anelectron-withdrawing anion source compound. Thus, the chemically-treatedsolid oxide compound comprises the calcined contact product of at leastone solid oxide compound with at least one electron-withdrawing anionsource compound. Typically, the chemically-treated solid oxide comprisesat least one ionizing, acidic solid oxide compound. The terms “support”and “activator-support” are not used to imply these components areinert, and such components should not be construed as an inert componentof the catalyst composition.

The organoaluminum compound used with the present disclosure may havethe formula:

(R³)₃Al;

in which (R³) is an aliphatic group having from 2 to about 6 carbonatoms. In some instances, (R³) is ethyl, propyl, butyl, hexyl, orisobutyl.

In an embodiment, the catalysts are chosen from compounds like thoserepresented by the chemical structures A and B with sulfated alumina asthe activator-support and with tri-isobutylaluminum (TIBA) as theco-catalyst.

The PE polymer and/or individual components of the PE polymer maycomprise a homopolymer, a copolymer, or blends thereof. In anembodiment, the PE polymer is a polymer of ethylene with one or morecomonomers such as alpha olefins. In an embodiment, the PE polymercomprises a higher molecular weight ethylene/1-olefin copolymer (HMW)component and a lower molecular weight ethylene/1-olefin copolymer (LMW)component. The comonomer of the HMW component of the PE polymer may bethe same as or different from the comonomer of the LMW component.Examples of suitable comonomers include without limitation unsaturatedhydrocarbons having from 3 to 20 carbon atoms such as propylene,1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 4-methyl-1-pentene,1-heptene, 1-octene, 1-nonene, 1-decene, and mixtures thereof. In anembodiment, the comonomer for the LMW component and HMW component of thePE polymer is 1-hexene. In an embodiment, the comonomer (e.g., 1-hexene)is present in an amount of greater than about 0.5 wt % to about 14 wt %,alternately from about 1 wt % to about 12 wt %, or alternately fromabout 2.5 wt % to about 8.5 wt % based on NMR analysis.

The PE polymer may be a unimodal resin, alternatively a multimodalresin. Herein, the “modality” of a polymer resin refers to the form ofits molecular weight distribution curve, i.e. the appearance of a graphof the polymer weight fraction, frequency, or number as a function ofits molecular weight. The polymer weight fraction refers to the weightfraction of molecules of a given size. A polymer resin may have two ormore components that may be distinguishable from one another, forexample based upon their individual composition and/or molecular weightdistribution. A molecular weight distribution curve may be prepared foreach individual component of the polymer resin.

The molecular weight distribution curves for the individual componentsmay be superimposed onto a common chart to form the weight distributioncurve for the polymer resin as a whole. Upon such superimposition, theresultant curve for the polymer resin as a whole may be multimodal orshow n distinct peaks corresponding to n polymer components of differingmolecular weight distributions. For example, a polymer having amolecular weight distribution curve showing a single peak may bereferred to as a unimodal polymer, a polymer having a curve showing twodistinct peaks may be referred to as a bimodal polymer, a polymer havinga curve showing three distinct peaks may be referred to as a trimodalpolymer, etc. Polymers having molecular weight distribution curvesshowing more than one peak may be collectively referred to as multimodalpolymers or resins. Furthermore, the distinct peaks may correspond tocomponents exhibiting distinct characteristics. For example, a bimodalpolymer resin may show two distinct peaks corresponding to twoindividual components of differing molecular weights.

In an embodiment, the PE polymer comprises a bimodal PE polymer. In suchembodiments, the LMW component may be present in an amount ranging fromabout 25% to about 95%, alternatively from about 40% to about 80% oralternatively from about 50% to about 75% while the HMW component may bepresent in an amount of from about 5% to about 75%, alternatively fromabout 20% to about 60% or alternatively from about 25% to about 50% withthe percentages being based on the total weight of the PE polymer. Theremainder of the discussion will focus on bimodal PE polymers with theunderstanding that other polymers, for example having differentmodality, may be employed in various aspects and embodiments as would beapparent to one skilled in the art with the benefits of this disclosure.

The PE polymers disclosed herein may have a variety of properties andparameters described below either singularly or in combination. Anysuitable methodology may be employed for determination of theseproperties and parameters.

In an embodiment, the LMW component of the PE polymer may have a weightaverage molecular weight (M_(w)) ranging from about 5,000 g/mol to about100,000 g/mol, alternatively from about 10,000 g/mol to about 80,000g/mol or alternatively from about 15,000 g/mol to about 60,000 g/molwhile the HMW component of the PE polymer may have a M_(w) ranging fromabout 300,000 g/mol to about 600,000 g/mol, alternatively from about325,000 g/mol to about 550,000 g/mol or alternatively from about 350,000g/mol to about 520,000 g/mol. The PE polymer as a whole may have a M, offrom about 150,000 g/mol to about 300,000 g/mol, alternatively, fromabout 170,000 g/mol to about 280,000 g/mol, or alternatively, from about190,000 g/mol to about 265,000 g/mol. The M_(w) may be calculatedaccording to equation 1:

$\begin{matrix}{{\overset{\_}{M}}_{w} = \frac{\sum\limits_{i}{N_{i}M_{i}^{2}}}{\sum\limits_{i}{N_{i}M_{i}}}} & (1)\end{matrix}$

where N_(i) is the number of molecules of molecular weight M_(i). Allmolecular weight averages are expressed in gram per mole (g/mol).

In an embodiment, the PE polymer may have a number average molecularweight (M_(n)) ranging from about 8,000 g/mol to about 35,000 g/mol,alternatively from about 9,000 g/mol to about 30,000 g/mol oralternatively from about 10,000 g/mol to about 25,000 g/mol. The M_(n)is the common average of the molecular weights of the individualpolymers calculated as shown in Equation 2 by measuring the molecularweight of n polymer molecules, summing the weights, and dividing by n.

$\begin{matrix}{{\overset{\_}{M}}_{n} = \frac{\sum\limits_{i}{N_{i}M_{i}}}{\sum\limits_{i}N_{i}}} & (2)\end{matrix}$

The molecular weight distribution (MWD) of the PE polymer may becharacterized by determining the ratio of the M_(w) to the M_(n), whichis also referred to as the polydispersity index (PDI) or more simply aspolydispersity. The PE polymers of this disclosure as a whole maydisplay a PDI of from about 4 to about 50, alternatively from about 5 toabout 40, or alternatively from about 6 to about 35.

The PE polymers of this disclosure may have a melt index (MI) under aforce of 2.16 kg of from about 0.01 dg/min to about 0.5 dg/min,alternatively from about 0.1 dg/min to about 0.5 dg/min, alternativelyfrom about 0.01 dg/min to about 0.3 dg/min, or alternatively from about0.01 dg/min to about 0.25 dg/min.

The PE polymers of this disclosure may have a melt index under a forceof 5 kg (15) of from about 0.01 dg/min to about 1 dg/min, alternativelyfrom about 0.01 dg/min to about 0.08 dg/min, or alternatively from about0.01 dg/min to about 0.07 dg/min.

The PE polymers of this disclosure may have a melt index under a forceof 10 kg (110) of from about 0.1 dg/min to about 5 dg/min, alternativelyfrom about 0.1 dg/min to about 3 dg/min, or alternatively from about 0.1dg/min to about 2.0 dg/min. The melt index (MI (12.16), 15, 110)represents the rate of flow of a molten resin through an orifice of0.0825 inch diameter when subjected to the indicated force at 190° C. asdetermined in accordance with ASTM D 1238.

The PE polymers of this disclosure may have a high load melt index(HLMI) of from about 4 dg/min to about 25 dg/min, alternatively fromabout 5 dg/min to about 20 dg/min, or alternatively from about 6 dg/minto about 16 dg/min. The HLMI represents the rate of flow of a moltenresin through an orifice of 0.0825 inch diameter when subjected to aforce of 21.6 kg at 190° C. as determined in accordance with ASTM D1238.

The PE polymers of this disclosure may be further characterized ashaving a density of from about 0.910 g/cc to about 0.940 g/cc,alternatively from about 0.920 g/cc to about 0.940 g/cc or alternativelyfrom about 0.925 g/cc to about 0.940 g/cc. The density refers to themass per unit volume of polymer and may be determined in accordance withASTM D1505.

The PE polymers of this disclosure may be further characterized by theirrheological breadth. Rheological breadth refers to the breadth of thetransition region between Newtonian and power-law type shear rate for apolymer or the frequency dependence of the viscosity of the polymer. Therheological breadth is a function of the relaxation time distribution ofa polymer resin, which in turn is a function of the resin molecularstructure or architecture. Assuming the Cox-Merz rule, the rheologicalbreadth may be calculated by fitting flow curves generated inlinear-viscoelastic dynamic oscillatory frequency sweep experiments witha modified Carreau-Yasuda (CY) model, which is represented by equation3:

$\begin{matrix}{E = {E_{o}\left\lbrack {1 + \left( {T_{\xi}\overset{.}{\gamma}} \right)^{a}} \right\rbrack}^{\frac{n - 1}{a}}} & (3)\end{matrix}$

where

E=viscosity (Pa·s)

{dot over (γ)}=shear rate (1/s)

a=rheological breadth parameter

T_(ξ)=relaxation time (s) [describes the location in time of thetransition region]

E_(o)=zero shear viscosity (Pa·s) [defines the Newtonian plateau]

n=power law constant [defines the final slope of the high shear rateregion].

To facilitate model fitting, the power law constant is held at aconstant value. Details of the significance and interpretation of the CYmodel and derived parameters may be found in: C. A. Hieber and H. H.Chiang, Rheol. Acta, 28, 321 (1989); C. A. Hieber and H. H. Chiang,Polym. Eng. Sci., 32, 931 (1992); and R. B. Bird, R. C. Armstrong and O.Hasseger, Dynamics of Polymeric Liquids, Volume 1, Fluid Mechanics, 2ndEdition, John Wiley & Sons (1987), each of which is incorporated byreference herein in its entirety.

In an embodiment, the PE polymer of this disclosure has an “eta zero”(E₀) value of from about 1×10⁴ Pa·s to about 5×10⁵ Pa·s, alternativelyfrom about 4×10⁴ Pa·s to about 3×10⁵ Pa·s, or alternatively from about6×10⁴ Pa·s to about 2.5×10⁵ Pa·s when the dynamic complex viscosityversus frequency scan are fitted to the Carreau-Yasuda equation with ann=0.1818 value.

In an embodiment, the PE polymer of this disclosure has an CY“a” valueof from about 0.35 to about 0.65, alternatively from about 0.38 to about0.63, or alternatively from about 0.40 to about 0.60 wherein the dynamiccomplex viscosity versus frequency scan are fitted to the Carreau-Yasudaequation with an n=0.1818 value.

In an embodiment, a PE polymer of this disclosure has an “tau eta”(T_(ξ)) value of from about 0.2 seconds (s) to about 5.0 s,alternatively from about 0.4 s to about 3.0 s, or alternatively fromabout 0.5 s to about 2.5 s wherein the dynamic complex viscosity versusfrequency scan are fitted to the Carreau-Yasuda equation with ann=0.1818 value.

In an embodiment, a PE polymer of this disclosure is fabricated into afilm. The films of this disclosure may be produced using any suitablemethodology. In an embodiment, the polymeric compositions are formedinto films through a blown film process. In a blown film process,plastic melt is extruded through an annular slit die, usuallyvertically, to form a thin walled tube. Air is introduced via a hole inthe center of the die to blow up the tube like a balloon. Mounted on topof the die, a high-speed air ring blows onto the hot film to cool it.The tube of film then continues upwards, continually cooling, until itpasses through nip rolls where the tube is flattened to create what isknown as a lay-flat tube of film. This lay-flat or collapsed tube isthen taken back down the extrusion tower via more rollers. On higheroutput lines, the air inside the bubble is also exchanged. This is knownas Internal Bubble Cooling (IBC).

The lay-flat film is then either kept as such or the edges of thelay-flat are slit off to produce two flat film sheets and wound up ontoreels. Typically, the expansion ratio between die and blown tube of filmwould be 1.5 to 4 times the die diameter. The films are extruded using“HDPE film” or “high-stalk extrusion” conditions with a neck height(freeze line height) to die diameter ratio from about 6:1 to 10:1. Thedrawdown between the melt wall thickness and the cooled film thicknessoccurs in both radial and longitudinal directions and is easilycontrolled by changing the volume of air inside the bubble and byaltering the haul off speed. The films formed from PE polymers of thisdisclosure may be of any thickness desired by the user. Alternatively,the PE polymers of this disclosure may be formed into films having athickness of from about 0.1 mils to about 8 mils, alternatively fromabout 0.2 mils to about 5 mils, or alternatively from about 0.3 mils toabout 3 mils.

Films formed from PE polymers of this disclosure may be characterized bya 1% secant modulus in the transverse direction (TD) of from about 300MPa to about 1200 MPa, alternatively from about 350 MPa to about 1100MPa, or alternatively from about 400 MPa to about 1050 MPa as determinedin accordance with ASTM D882.

In an embodiment, the films formed from PE polymers of this disclosuremay be characterized by a 1% secant modulus in the machine direction(MD) of from about 350 MPa to about 800 MPa, alternatively from about350 MPa to about 750 MPa, or alternatively from about 400 MPa to about700 MPa as determined in accordance with ASTM D882, using a testspecimen having a 1.0 mil thickness. The secant modulus is a measure ofthe rigidity or stiffness of a material. It is basically the appliedtensile stress, based on the force and cross-sectional area, divided bythe observed strain at that stress level. It is generally constantbefore the material approaches the point at which permanent deformationwill begin to occur.

In an embodiment, the films formed from PE polymers of this disclosuremay display enhanced toughness and tear properties. In an embodiment,the films formed from PE polymers of this disclosure may display anincreased impact strength as indicated by an increased dart dropstrength. The dart drop strength refers to the weight required to cause50% of tested films to fail by impact from a falling dart underspecified test conditions. Specifically, one method employs the use of adart having a 38 mm (1.5 in) head diameter dropped from a height of 0.66m (26. in). In an aspect, films formed from PE polymers of thisdisclosure have a dart drop strength, also termed a dart impactstrength, of greater than about 175 g, alternatively greater than about200 g as measured in accordance with ASTM D1709 Method A using a testspecimen having a 1 mil thickness. In an alternative embodiment, thefilms formed from the PE polymers of this disclosure have a dart dropstrength ranging from about 100 g to about 900 g, alternatively fromabout 150 g to about 850 g or alternatively from about 200 g to about800 g as measured in accordance with ASTM D1709 Method A using a testspecimen having a 1 mil thickness.

In an embodiment, the films formed from PE polymers of this disclosuremay display increased tear strength as indicated by an increasedElmendorf tear strength. The Elmendorf tear strength refers to theaverage force required to propagate tearing through a specified lengthof plastic film or nonrigid sheeting on an Elmendorf-type tear tester.Specifically, test specimens having a pre-cut slit are contacted with aknife-tipped pendulum. The average force required to propagate tearingis calculated from the pendulum energy lost while tearing the testspecimen. The tear may be propagated either in the MD or TD. In anembodiment, films formed from PE polymers of this disclosure have anElmendorf tear strength in the MD of greater than about 20 g,alternatively greater than about 100 g. In an embodiment, films formedfrom PE polymers of this disclosure have an Elmendorf tear strength inthe TD of greater than about 475 g, alternatively greater than about 550g. In an alternative embodiment, the films formed from the PE polymersof this disclosure have an Elmendorf tear strength in the MD of fromabout 10 g to about 130 g, alternatively from about 10 g to about 110 g,or alternatively from about 15 g to about 100 g and an Elmendorf tearstrength in the TD ranging from about 300 g to about 1000 g,alternatively from about 350 g to about 900 g, or alternatively fromabout 400 g to about 850 g as measured in accordance with ASTM D1922using a test specimen having a 1.0 mil thickness.

In an embodiment, the films formed from PE polymers of this disclosuremay display an increased impact strength as indicated by an increasedSpencer impact. Spencer impact measures the energy necessary to burstand penetrate the center of a specimen, mounted between two rings with a3.5 inch diameter. The following equation, equation 4, may be used toobtain an impact value in joules:

E=RC/100  (4)

where E is the energy to rupture, Joules, C is the apparatus capacityand, R is the scale reading on a 0 to 100 scale. In an embodiment, thefilms formed from the PE polymers of this disclosure have a Spencerimpact of from about 0.25 J to about 2.5 J, alternatively from about 0.3J to about 2.3 J, or alternatively from about 0.5 J to about 2 J asmeasured in accordance with ASTM D3420 using a test specimen having a 1mil thickness.

In an embodiment, films formed from the PE polymers of this disclosureare characterized by a TD yield strength ranging from about 1400 psi toabout 5800 psi, alternatively from about 1700 psi to about 5000 psi, oralternatively from about 2000 psi to about 4500 psi. In an embodiment,films formed from the PE polymers of this disclosure are characterizedby a TD yield strain ranging from about 2% to about 15%, alternativelyfrom about 3% to about 13%, or alternatively from about 3.5% to about12%. In an embodiment, films formed from the PE polymers of thisdisclosure are characterized by a TD break strength ranging from about4300 psi to about 10000 psi alternatively from about 5000 psi to about9000 psi, or alternatively from about 5500 psi to about 8500 psi.

In an embodiment, films formed from the PE polymers of this disclosureare characterized by a break strength in the MD ranging from about 6500psi to about 13500 psi, alternatively from about 7000 psi to about 13000psi, or alternatively from about 8000 psi to about 12500 psi. In anembodiment, films formed from the PE polymers of this disclosure arecharacterized by a MD yield strain of less than about 8%, alternativelyfrom about 2% to about 7.5%, or alternatively from about 4% to about7.0%. The yield strength refers to the stress a material can withstandwithout permanent deformation of the material while the yield strainrefers to amount of deformation elongation that occurs without permanentdeformation of the material. The break strength refers to the tensilestress corresponding to the point of rupture while the MD break strainrefers to the tensile elongation in the machine direction correspondingto the point of rupture. The yield strength, yield strain, breakstrength, break strain in the MD may be determined in accordance withASTM D882. In an embodiment, the sum of the MD yield strain and TD yieldstrain is less than about 15%, alternatively less than about 14.5%, oralternatively less than about 14%.

In an embodiment, films formed from the PE polymers of this disclosureare characterized by a haze of greater than about 60%, alternativelygreater than about 70%, alternatively greater than about 80%, oralternatively greater than about 90%. Haze is the cloudy appearance of amaterial caused by light scattered from within the material or from itssurface. The haze of a material can be determined in accordance withASTM D1003.

In an embodiment, the films formed from PE polymers of this disclosuremay display characteristic oxygen transmission rates (OTR) and/ormoisture vapor transmission rates (MVTR). OTR is the measurement of theamount of oxygen gas that passes through a film over a given period.Testing may be conducted under a range of relative humidity conditionsat a range of temperatures. Typically, one side of the film is exposedto the oxygen permeant. As it solubilizes into the film and permeatesthrough the sample material, nitrogen sweeps the opposite side of thefilm and transports the transmitted oxygen molecules to a coulometricsensor. This value is reported as a transmission rate. When this rate ismultiplied by the average thickness of the material, the results areconsidered a permeability rate. In an embodiment, the films formed fromthe PE polymers of this disclosure have an OTR of less than about 525cc/100 in² alternatively less than about 500 cc/100 in² alternativelyfrom about less than about 475 cc/100 in² for a 1-mil film as measuredin accordance with ASTM D3985.

The MVTR measures passage of gaseous H₂O through a barrier. The MVTR mayalso be referred to as the water vapor transmission rate (WVTR).Typically, the MVTR is measured in a special chamber, divided verticallyby the substrate/barrier material. A dry atmosphere is in one chamber,and a moist atmosphere is in the other. A 24-hour test is run to see howmuch moisture passes through the substrate/barrier from the “wet”chamber to the “dry” chamber under conditions which can specify any oneof five combinations of temperature and humidity in the “wet” chamber.In an embodiment, the films formed from the PE polymers of thisdisclosure have an MVTR of less than about 1.3 g-mil/100 in²-day;alternatively less than about 1.1 g-mil/100 in²-day or alternativelyless than about 1 g-mil/100 in²-day for 1-mil film as measured inaccordance with ASTM F 1249 at 100° F. and 90% relative humidity (RH).

In an embodiment, the films produced by the compositions and methods ofthis disclosure display a unique combination of impact properties andtear strength at the disclosed densities. The films of this disclosuremay be used in the formation of any variety of end-use articles such asfor example merchandise bags, t-shirt bags, trash can liners, grocerysacks, produce bags, food packaging for contents such as cereals,crackers, cheese, meat, etc.

EXAMPLES

The invention having been generally described, the following examplesare given as particular embodiments of the invention and to demonstratethe practice and advantages thereof. It is understood that the examplesare given by way of illustration and are not intended to limit thespecification of the claims in any manner.

Example 1

Two experimental resins, designated Samples A and B, were prepared usingdiffering dual metallocene catalysts under conditions of the typedisclosed herein. The resin density, HLMI and MI are presented inTable 1. COMP-1 is a typical commercial unimodal resin of mediumdensity.

TABLE 1 Sample Density (g/cc) MI (dg/min.) HLMI (dg/min.) COMP-1 0.93740.26 22.1 INV-A 0.9377 0.09 10.4 INV-B 0.9409 0.12 27.2

The three resins from Table 1 were formed into blown films using a BGEblown film with internal bubble cooling and a 6-inch die, 0.040 inch diegap, at an output rate of 250 lb/hr, a 4:1 blow up ratio (BUR), a 42inch freeze line (neck) height (7:1 freeze line height to die diameterratio), a flat set extrusion temperature profile of 210° C. across theextruder and die and 1.0 mil gauge. The thickness of the film may alsobe referred to as the film gauge. The dart and tear properties of theblown film were evaluated and are presented in Table 2.

TABLE 2 Dart Drop Spencer MD Tear TD Tear Sample (g) (J) (g) (g) COMP-152 0.40 19 676 INV-A 226 1.26 30 944 INV-B 188 0.64 23 467

The tensile properties of the blown film were further investigated andthat data is presented in Table 3.

TABLE 3 MD MD MD MD TD TD TD TD MD Break Break Yield Yield TD BreakBreak Yield Yield Modulus Strain Strength Strain Strength Modulus StrainStrength Strain Strength Sample psi % psi % psi psi % psi % psi COMP-180,597 472 9,063 17 2,977 106,083 739 7,055 11 3,371 INV-A 83,489 2827,998 16 3,208 127,500 572 5,701 9 3,329 INV-B 68,579 306 4,830 13 2,701 91,422 527 3,433 8 2,501

The data indicated that compared to a conventional MDPE (i.e., SampleCOMP-1), Samples INV-A and INV-B, which are PE polymers of the typedisclosed herein (i.e., PITs), displayed impact properties that werenearly four times greater than that of a conventional MDPE resin. Forboth Samples INV-A and INV-B the MD tear strength of the films washigher than that of Sample COMP-1. For Sample INV-A, the TD tearstrength was considerably greater than Sample COMP-1 while stillexhibiting higher dart drop and MD tear strength.

Additional samples of PE resins of the type disclosed herein wereprepared on a 1.5″ Davis-Standard Blown Film line equipped with Sano diehaving 2 inch die diameter, a 0.035 inch die gap at a 4:1 BUR and a 14inch freeze line (neck) height and a flat set extrusion temperatureprofile of 205° C. across the extruder and die, an output rate of 30lb/hr and 1-mil gauge. The resin density, HLMI, and properties of thefilms are presented in Table 4. Sample COMP-1 was a typical commercialunimodal resin of medium density and was used as a control.

TABLE 4 Pellet HLMI, Dart MD Tear TD Tear Sample Density (g/cc) (dg/min)(g) (g) (g) INV-E 0.9273 17.8 259 88 672 INV-G 0.9352 9.5 261 88 553INV-H 0.9386 15.0 200 86 589 INV-I 0.9364 10.1 314 82 532 INV-J 0.94109.5 219 79 763 INV-K 0.9366 5.4 494 47 768 INV-L 0.9382 9.2 248 54 799INV-M 0.9382 8.6 246 33 801 INV-N 0.9371 5.8 415 46 648 COMP-1 0.938523.1 71 62 543

Several of the samples listed in Table 4 were also formed into blownfilm having a thickness of 0.5 mils. Downgauging to thinner gauge didnot impact bubble stability. The impact strength properties of the filmsat 1.0 and 0.5 mils are presented in Table 5 and demonstrate that theproperties stayed high at lower gauges.

TABLE 5 Film Dart Impact MD Tear TD Tear Sample Gauge (mil) (g) (g) (g)COMP-1 1.0 112 31 751 INV-I-1 1.0 200 86 589 INV-I-2 0.5 183 19 387INV-J-1 1.0 314 82 532 INV-J-2 0.5 258 21 342 INV-H-1 1.0 261 88 553INV-H-2 0.5 238 21 313 INV-K-1 1.0 219 79 763 INV-K-2 0.5 279 21 399

The results indicate that films formed from PE polymers of the typedisclosed herein exhibit high toughness as evidenced by the tear andimpact properties even at a film gauge of 0.5 mil. In contrast theconventional MDPE resin, Sample COMP-1, could not be converted into a0.5 mil film due to poor bubble stability. PE polymers of the typedisclosed herein can be advantageously downgauged while retaining theirimpact properties and tear strength.

Additional properties of the samples were investigated and the resultsare presented in Tables 6-8. Samples COMP-1a and COMP-1b were obtainedfrom two differing batches of comparative sample COMP-1.

TABLE 6 Zero HLMI MD TD Shear (dg/min) Tear Tear Haze Gloss Viscositytau M_(n) M_(w) M_(z) Sample — (g) (g) (%) 60% (Pa-s) (s) CY-a (kg/mol)(kg/mol) (kg/mol) M_(w)/M_(n) INV-G 9.5 88 553 80 10 7.4E+04 0.53060.5419 12.1 201.3 701.9 16.7 INV-H 15.0 86 589 84 9 6.7E+04 0.53560.5296 10.6 192.2 724.6 18.2 INV-I 10.1 82 532 79 10 7.3E+04 0.51370.5425 11.9 200.3 687.1 16.8 INV-J 9.5 79 763 77 11 8.7E+04 0.56190.5155 11.7 208.1 737.5 17.8 INV-K 5.4 47 768 90 n/a 1.4E+05 0.98740.5262 31.2 242.8 715 7.8 INV-L 9.2 54 799 92 n/a 1.0E+05 0.8400 0.461131.6 217.1 675 6.9 INV-M 8.6 33 801 92 n/a 1.1E+05 0.8674 0.4705 26.9224.2 727 8.3 INV-N 5.8 46 648 90 n/a 1.4E+05 0.9975 0.5034 25.6 230.2735 9.0 COMP-1a 23.1 62 543 53 n/a 3.6E+05 0.9317 0.1778 12.1 186.5 122015.4 COMP- 24.1 56 700 59 15 3.1E+05 0.822 0.1836 13.1 195.0 1649.4 14.91b

TABLE 7 MD MD MD Tensile MD Tensile MD 1% MD 2% Yield Yield Break BreakMD Secant Secant Strain Strength Strain Strength Modulus Modulus ModulusSample (%) (psi) (%) (psi) (psi) (psi) (psi) INV-K 5.4 3,124 254 11,542106,400 96,356 78,726 INV-L 4.6 3,000 333 10,347 106,319 95,379 77,297INV-M 4.6 3,034 287 10,002 105,969 98,246 79,817 INV-N 5.0 3,172 25612,020 108,376 99,268 81,479 COMP-1 68.4  3,626 493  8,037  91,60382,650 66,165

TABLE 8 TD TD TD Tensile Tensile TD 1% TD 1% TD 2% Yield TD Yield TDYield Break Break TD TD Secant Secant Secant Strain Strength StrengthStrain Strength Modulus Modulus Modulus Modulus Modulus Sample (%) (psi)(MPa) (%) (psi) (psi) (MPa) (psi) (MPa) (psi) INV-K 3.9 3,718 25.6 5056,878 169,562 1,169 146,910 1,013 112,320 INV-L 4.0 3,832 26.4 603 7,249166,246 1,146 145,237 1,001 112,082 INV-M 3.9 3,864 26.6 570 6,721170,351 1,175 148,320 1,023 113,967 INV-N 3.6 3,805 26.2 545 7,647168,613 1,163 146,068 1,007 111,707 COMP-1 7.2 3,261 22.5 622 6,531108,688  749  93,338  644  71,292

ADDITIONAL DISCLOSURE

The following enumerated embodiments are provided as non-limitingexamples.

A first embodiment which is an ethylene alpha-olefin copolymer having(a) a density of from about 0.910 g/cc to about 0.940 g/cc; (b) a weightaverage molecular weight of from about 150,000 g/mol to about 300,000g/mol; and (c) a melt index at a load of 2.16 kg of from about 0.01dg/10 min. to about 0.5 dg/min.; wherein a 1 mil blown film formed fromthe polymer composition is characterized by (i) a Dart Impact strengthgreater than about 175 g/mil; (ii) an Elmendorf machine direction tearstrength greater than about 20 g/mil; and (iii) an Elmendorf transversedirection tear strength greater than about 475 g/mil.

A second embodiment which is the copolymer of the first embodimenthaving a higher molecular weight component and a lower molecular weightcomponent.

A third embodiment which is the copolymer of the second embodimentwherein the lower molecular weight component has a weight averagemolecular weight of from about 5,000 g/mol to about 100,000 g/mol.

A fourth embodiment which is the copolymer of any one of the secondthrough third embodiments wherein the higher molecular weight componenthas a weight average molecular weight of from about 300,000 g/mol toabout 600,000 g/mol.

A fifth embodiment which is the copolymer of any one of the firstthrough fourth embodiments having a number average molecular weight offrom about 8,000 g/mol to about 35,000 g/mol.

A sixth embodiment which is the copolymer of any one of the firstthrough fifth embodiments having a molecular weight distribution of fromabout 4 to about 30.

A seventh embodiment which is the copolymer of any one of the firstthrough sixth embodiments having a Eta(0) value of from about 1×10⁴ Pa·sto about 5×10⁵ Pa·s.

An eighth embodiment which is the copolymer of any one of the firstthrough seventh embodiments having a tau-eta value of from about 0.2 sto about 5 s.

A ninth embodiment which is the copolymer of any one of the firstthrough eighth embodiments having a CY-a value of from about 0.35 toabout 0.65.

A tenth embodiment which is the copolymer of any one of the firstthrough ninth embodiments having a melt index at a load of 5.0 kg offrom about 0.01 dg/min. to about 1 dg/min.

An eleventh embodiment which is the copolymer of any one of the firstthrough tenth embodiments having a melt index at a load of 10.0 kg offrom about 0.01 dg/min. to about 5 dg/min.

A twelfth embodiment which is the copolymer of any one of the firstthrough eleventh embodiments having a high-load melt index at a load of21.6 kg of from about 4 dg/min to about 25 dg/min.

A thirteenth embodiment which is the copolymer of any one of the firstthrough twelfth embodiments having a yield strain in the machinedirection of less than about 8%.

A fourteenth embodiment which is the copolymer of any one of the firstthrough thirteenth embodiments having a sum of the yield strain in themachine direction and yield strain in the transverse direction of lessthan about 15%.

A fifteenth embodiment which is the copolymer of any one of the firstthrough fourteenth embodiments wherein the copolymer comprises 1-butene,1-pentene, 1-hexene, 3-methyl-1-butene, 4-methyl-1-pentene, 1-heptene,1-octene, 1-nonene, 1-decene or combinations thereof.

A sixteenth embodiment which is a film formed from the copolymer of anyone of the first through fifteenth embodiments having a Spencer impactof from about 0.25 J to about 2.5 J.

A seventeenth embodiment which is the film of the sixteenth embodimenthaving a haze value of greater than about 70%.

An eighteenth embodiment which is the film of the sixteenth embodimenthaving a haze value of greater than about 80%.

A nineteenth embodiment which is an ethylene alpha-olefin copolymerhaving (a) a density of from about 0.910 g/cc to about 0.940; (b) aweight average molecular weight of from about 150,000 g/mol to about300,000 g/mol; and (c) a melt index at a load of 2.16 kg of from about0.01 dg/10 min. to about 0.5 dg/min.; wherein a 1 mil blown film formedfrom the copolymer has (i) a Dart Impact strength greater than about 200g/mil, (ii) an Elmendorf machine direction tear strength less than about100 g/mil and (iii) an Elmendorf transverse direction tear strengthgreater than about 550 g/mil.

A twentieth embodiment which is an ethylene alpha-olefin copolymerhaving a density of from about 0.910 g/cc to about 0.940 g/cc; a weightaverage molecular weight of from about 150,000 g/mol to about 300,000g/mol; a melt index at a load of 2.16 kg of from about 0.01 dg/min. toabout 0.5 dg/min.; a melt index at a load of 5.0 kg of from about 0.01dg/min. to about 1 dg/min.; a melt index at a load of 10.0 kg of fromabout 0.01 dg/min. to about 5 dg/min; and a high-load melt index at aload of 21.6 kg of from about 4 dg/min to 25 dg/min, wherein a 1-milblown film formed from the polymer composition has an Elmendorf tearstrength in the machine direction of from about 10 g to about 130 g asdetermined in accordance with ASTM D1922.

A twenty-first embodiment which is the copolymer of the twentiethembodiment, wherein the blown film has a dart drop impact strength,measured in accordance with ASTM D1709 Method A, of from about 100 g toabout 900 g.

Without further elaboration, it is believed that one skilled in the artcan, using the description herein, utilize the present invention to itsfullest extent. While inventive aspects have been shown and described,modifications thereof can be made by one skilled in the art withoutdeparting from the spirit and teachings of the invention. Theembodiments and examples described herein are exemplary only, and arenot intended to be limiting. Many variations and modifications of theinvention disclosed herein are possible and are within the scope of theinvention. Where numerical ranges or limitations are expressly stated,such express ranges or limitations should be understood to includeiterative ranges or limitations of like magnitude falling within theexpressly stated ranges or limitations (e.g., from about 1 to about 10includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13,etc.). Use of the term “optionally” with respect to any element of aclaim is intended to mean that the subject element is required, oralternatively, is not required. Both alternatives are intended to bewithin the scope of the claim. Use of broader terms such as comprises,includes, having, etc. should be understood to provide support fornarrower terms such as consisting of, consisting essentially of,comprised substantially of, etc.

Accordingly, the scope of protection is not limited by the descriptionset out above but is only limited by the claims which follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated into the specification as an embodiment ofthe present invention. Thus, the claims are a further description andare an addition to the embodiments of the present invention. Thedisclosures of all patents, patent applications, and publications citedherein are hereby incorporated by reference, to the extent that theyprovide exemplary, procedural or other details supplementary to thoseset forth herein.

What is claimed is:
 1. An ethylene alpha-olefin copolymer having: (a) adensity of from about 0.910 g/cc to about 0.940 g/cc; (b) a weightaverage molecular weight of from about 150,000 g/mol to about 300,000g/mol wherein the copolymer comprises a metallocene-catalyzed copolymerhaving a higher molecular weight component and a lower molecular weightcomponent and wherein the lower molecular weight component has a weightaverage molecular weight of from about 5,000 g/mol to about 100,000g/mol; and (c) a melt index at a load of 2.16 kg of from about 0.01dg/min. to about 0.5 dg/min; wherein the copolymer is characterized by(i) a Dart Impact strength greater than about 175 g/mil when tested inaccordance with ASTM D1709 Method A using a test specimen having a 1 milthickness; (ii) an Elmendorf machine direction tear strength greaterthan about 20 g/mil when tested in accordance with ASTM D1922 using atest specimen having a 1 mil thickness; and (iii) an Elmendorftransverse direction tear strength greater than about 475 g/mil whentested in accordance with ASTM D1922 using a test specimen having a 1mil thickness. 2-3. (canceled)
 4. The copolymer of claim 1 wherein thehigher molecular weight component has a weight average molecular weightof from about 300,000 g/mol to about 600,000 g/mol.
 5. The copolymer ofclaim 1 having a number average molecular weight of from about 8,000g/mol to about 35,000 g/mol.
 6. The copolymer of claim 1 having amolecular weight distribution of from about 4 to about
 30. 7. Thecopolymer of claim 1 having a Eta(0) value of from about 1×10⁴ Pa·s toabout 5×10⁵ Pa·s.
 8. The copolymer of claim 1 having a tau-eta value offrom about 0.2 s to about 5 s.
 9. The copolymer of claim 1 having a CY-avalue of from about 0.35 to about 0.65.
 10. The copolymer of claim 1having a melt index at a load of 5.0 kg of from about 0.01 dg/min. toabout 1 dg/min.
 11. The copolymer of claim 1 having a melt index at aload of 10.0 kg of from about 0.01 dg/min. to about 5 dg/min.
 12. Thecopolymer of claim 1 having a high-load melt index at a load of 21.6 kgof from about 4 dg/min to about 25 dg/min.
 13. The copolymer of claim 1having a yield strain in the machine direction of less than about 8%when tested in accordance with ASTM D882.
 14. The copolymer of claim 1having a sum of the yield strain in the machine direction and yieldstrain in the transverse direction of less than about 15% when tested inaccordance with ASTM D882.
 15. The copolymer of claim 1 wherein thecopolymer comprises 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene,4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene orcombinations thereof.
 16. The copolymer of claim 1 having a Spencerimpact of from about 0.25 J to about 2.5 J when tested in accordancewith ASTM D3420 using a test specimen having a 1 mil thickness.
 17. Thecopolymer of claim 1 having a haze value of greater than about 70% %when tested in accordance with ASTM D1003.
 18. The copolymer of claim 1having a haze value of greater than about 80% when tested in accordancewith ASTM D1003.
 19. An ethylene alpha-olefin copolymer having: (a) adensity of from about 0.910 glee to about 0.940 glee; (b) a weightaverage molecular weight of from about 150,000 g/mol to about 300,000g/mol; and (c) a melt index at a load of 2.16 kg of from about 0.01dg/min. to about 0.5 dg/min. wherein the copolymer comprises ametallocene-catalyzed copolymer having a higher molecular weightcomponent and a lower molecular weight component and wherein the lowermolecular weight component has a weight average molecular weight of fromabout 5,000 g/mol to about 100,000 g/mol; wherein the polymercomposition has (i) a Dart Impact strength greater than about 200 g/milwhen tested in accordance with ASTM D1709 Method A using a test specimenhaving a 1 mil thickness; (ii) an Elmendorf machine direction tearstrength greater than about 100 g/mil when tested in accordance withASTM D1922 using a test specimen having a 1 mil thickness; and (iii) anElmendorf transverse direction tear strength greater than about 550g/mil when tested in accordance with ASTM D1922 using a test specimenhaving a 1 mil thickness.
 20. An ethylene alpha-olefin copolymer having:a density of from about 0.910 g/cc to about 0.940 g/cc; a weight averagemolecular weight of from about 150,000 g/mol to about 300,000 g/mol; amelt index at a load of 2.16 kg of from about 0.01 dg/min. to about 0.5dg/min.; a melt index at a load of 5.0 kg of from about 0.01 dg/min. toabout 1 dg/min.; a melt index at a load of 10.0 kg of from about 0.01dg/min. to about 5 dg/min; and a high-load melt index at a load of 21.6kg of from about 4 dg/min to about 25 dg/min wherein the copolymercomprises a metallocene-catalyzed copolymer having a higher molecularweight component and a lower molecular weight component and wherein thelower molecular weight component has a weight average molecular weightof from about 5,000 g/mol to about 100,000 g/mol, wherein the polymercomposition has an Elmendorf tear strength in the machine direction offrom about 10 g to about 130 g as determined in accordance with ASTMD1922 using a test specimen having a 1 mil thickness and a dart dropimpact strength, tested in accordance with ASTM D1709 Method A, of fromabout 100 g to about 900 g using a test specimen having a 1 milthickness.
 21. (canceled)
 22. A film prepared from the copolymer ofclaim
 1. 23. The film of claim 22 having an oxygen transmission rate ofless than about 525 cc/100 in².
 24. The copolymer of claim 19 having anoxygen transmission rate of less than about 525 cc/100 in² when testedin accordance with ASTM D3985 using a test specimen having a 1 milthickness.